This invention relates to carbon black reactors. In one of its aspects it relates to methods for producing carbon black. In more specific aspects it relates to carbon black reactors having choke means within the reactant flow chambers of the reactors. In anotheraspect it relates to the production of low tint residual carbon black.
Tint residual (or tint residue) is a property of the carbon black defined by the following formula: EQU TR=T-[56.0+1.057 (CTAB)-0.002745 (CTAB).sup.2 -0.2596(DBP)-0.201 (N.sub.2 SA-CTAB)]
In this formula, the abbreviations used have the following meanings and the properties are measured as described:
TR: This is tint residual. PA1 CTAB: This is the surface area of the carbon black measured in accordance with ASTM D 3765-79, m.sup.2 /gm. PA1 N.sub.2 SA: This is the surface area of the carbon black measured using nitrogen in accordance with the ASTM method D-3037-71T, m.sup.2 /gm. PA1 Compressed DBP: This is the structure of the carbon black in cc/100 g and is measured in accordance with ASTM D 3493-76 This property is also referred to as 24M4 DBP. PA1 T: This is the tint or tinting strength of the carbon black measured related to the reference black IRB No. 3 which has an arbitrarily assigned value of 100. Tint is measured in accordance with ASTM 3265-75. PA1 CTAB: 73 to 140 square meters/gram PA1 Compressed DBP: 67 to 111 cc/100 g PA1 (N.sub.2 SA-CTAB): 23 square meters/gram or less
Among the carbon blacks defined by the formula given above, those that are further characterized by having surface area and structure properties within the following ranges are particularly preferred:
All these properties, namely Tint, CTAB, Compressed DBP and N.sub.2 SA, are defined and measured by ASTM procedures, as disclosed above.
It has been found that carbon black of low tint residual, particularly of tint residual in a range below -6, is desirable in the production of rubber compositions used in automobile tires because of low hysteresis, or heat buildup, under road conditions which high abrasion resistance of the compounds is retained. The production of low tint residual carbon black has, therefore, become increasingly important.
Carbon black can be produced by providing reaction conditions under which the flow pattern or the amount of flow of reactants is sufficiently disrupted during a production run to vary the surface area of the product by, among other things, affecting the aggregation of carbon black nodules so that aggregates of varying size result. The present invention provides apparatus and method for producing such a disruption of reactant flow as to effect the production of low tint residual carbon black.
It is, therefore, an object of this invention to provide apparatus and method for producing low tint residual carbon black. It is another object to provide apparatus for reciprocating a choke means within a carbon black reactor.
Other aspects, objects and the various advantages of this invention will become apparent after study of this specification, the drawing, and the appended claims.